Liquid fuel supply assembly



Oct. 29, 1968 s. COLE 3,408,152

LIQUID FUEL SUPPLY ASSEMBLY Filed April 5, 1967 a 22 2 j 25 L5 0 1 0 0 ,43

VIIIIIIIIIIIIIIAA INVENTOR. Saxon Co/e United States Patent 3,408,152 LIQUID FUEL SUPPLY ASSEMBLY Saxon Cole, Shrewsbury, Mo., assignor to American Air Filter Company, Inc., Louisville, Ky., a corporation of Delaware Filed Apr. 3, 1967, Ser. No. 628,036 7 Claims. (Cl. 431--89) ABSTRACT OF THE DISCLOSURE A liquid fuel burning combustor assembly having vapor eliminator means in the fuel supply conduit to eliminate vapors from the fuel stream before the fuel is sprayed into the combustor, and means whereby the separated vapors are conducted to the combustor to be mixed with flames and products of combustion in the combustor.

Background of the invention The present invention recognizes that in high performance liquid fuel burning combustors where a stream of liquid fuel is sprayed into a combustion chamber through a fuel spray nozzle, vapor bubbles'which from time to time appear in the fuel stream displace liquid fuel which would otherwise be supplied to the combustor and cause serious flame instability with resulting noise and smoking. The present invention further recognizes that the vapor bubbles can be composed of air, vaporized fuel, or other gases and even though the components of the vapor bubbles may be combustible, for example vaporized fuel, such bubbles reduce the total available fuel in the combustor and induce erratic operation and flame instability because the combustion rate is decreased.

Previous liquid fuel burning combustor assemblies have in most cases not recognized the consequences of burner operation with vapor-laden liquid fuel. In instances where it has been recognized that vapor bubbles may undesirably be present in a liquid fuel supply conduit, usually in the fuel supply systems for internal combustion engines, the devices provided to eliminate the vapor have been directed to the prevention of vapor lock in the fuel supply conduit rather than the elimination of very small quantities of vapor which, as the present invention now recognizes, are associated with flame instability in combustion devices. In such previous apparatus liquid fuel which may from time to time pass through the vapor eliminator adversely affects the operation of the combustion device.

Summary of the invention The present invention provides an effective arrangement for a liquid fuel vapor eliminator assembly for the fuel supply conduit of a combustor which is economical to manufacture and substantially improves the operation of combustion devices which burn liquid fuel.

Recognizing certain deficiencies in fuel supply systems for previous combustion devices the present invention provides a vapor eliminator in the fuel supply conduit upstream of the burner nozzle and a vapor bleed line to conduct vapors from the vapor eliminator directly into the combustion chamber. The vapors are consumed by the flames and hot gases generated in the combustion chamber to improve the efficiency of operation of the apparatus by advantageous utilization of such vapors and operation is not adversely affected by liquid fuel which may from time to time escape from the vapor eliminator into the vapor bleed line.

Various other features of the present invention will become obvious to one skilled in the art upon reading the disclosure set forth hereinafter.

More particularly, the present invention provides a liquid fuel burning combustor comprising a casing defining a combustion chamber for burning liquid fuel, a liquid fuel spray nozzle to supply a spray of fuel to the combus tion chamber, means to supply combustion air to the combustion chamber, a source of fuel for the nozzle, and an improved fuel supply means including: a fuel carrying conduit communicating with the fuel spray nozzle and the source of fuel; vapor eliminator means communicatively connected with the conduit means to remove vapor carried by the stream of fuel supplied by the fuel supply source; and, vapor conduit means communicating with the vapor eliminator means and the combustor to conduct vapor from the eliminator means to the combustor means.

It is to be understood that the description of one example of the present invention given herein is not by way of limitation and that various changes can be made in the arragement, form, or configuration of the apparatus disclosed herein without departing from the scope or spirit of the present invention.

Referring to the drawings which show one example of the present invention:

FIGURE 1 is a schematic diagram of one example of an apparatus in accordance with the present invention;

FIGURE 2 is an enlarged view, in section, of an example of a fuel spray nozzle assembly; and,

FIGURE 3 is an example of another arrangement in accordance with the present invention.

Combustion chamber and fuel supply arrangements in accordance with the present invention can be provided to supply heat for a selected application, for example in an air heater to heat a stream of air passed through the heater in heat exchange relation with the products of com bustion from the combustor. The invention will be described in terms of the example apparatus shown in the drawings which includes a combustion chamber housing 1 connected to a source of fuel (not shown) by a fuel conduit 22 including a communicatively connected vapor eliminator 14.

In the example of FIGURE 1 a combustion chamber casing 1 is provided and defines a combustion chamber 2. Casing 1 includes apertures 5 for admission of combustion air to chamber 2 and can be disposed within a somewhat larger casing 7 to define an annular air inlet 4 and an annular combustion air chamber 6 between casings 1 and 7. Combustion air is supplied through chamber 6 to combustor 1, for example by cooperative fan means (not shown).

Combustor casing 1 is adapted to be joined to a wall 8 of the particular apparatus which is to be heated by combustor assembly and, as shown, casing 1 can be joined to wall 8 in communicative aligned relation with an inlet 3 which is provided to receive flames and products of combustion emitted from chamber 2.

It has been recognized that vapor bubbles are undesirably released from liquid fuel for various reasons including increased temperature or decreased pressure which vaporizes a portion of the fuel and releases entrained air or other gases and in accordance with the present invention a vapor eliminator 14 is provided in communication with fuel conduit 22 which conducts fuel from the fuel supply means 25 to the spray assembly 9. In the example of the drawings vapor eliminator 14 includes two interconnected chambers 16 and 18 defined by a casing 14 where chamber 18 is normally filled with liquid fuel and the chamber 16 is adapted to receive a small float 17. The specific gravity of float 17 is, advantageously, less than the specific gravity of the liquid fuel but greater than the specific gravity of the vaporized fuel so the float will rise with increasing liquid level in chamber 18 but will fall in an atmosphere of vaporized fuel. Adjacent the upper portion of chamber 18 restrictions 21 are provided to define an outlet opening 210 having a diameter less 3 than the diameter of float 17 so the float is retained within chamber 16. A float seat 19 is provided adjacent outlet opening 19a from chamber 16 and, advantageously, is adapted to conform to the shape of float 17 so that when float 17 is urged against seat 19 by the buoyant forces of the liquid fuel opening 2111 from chamber 16 is closed.

A vapor line 13 is communicatively connected with opening 19a of chamber 16 and the other end likewise communicates with combustion chamber casing 1 to conduct vapors from vapor eliminator 14 to combustion chamber 2. It is to be noted that liquid fuel which may from time to time inadvertently leak past float 17 of vapor eliminator 14 is conducted directly to the combustion chamber and is immediately consumed without undesirably affecting the fuel-air ratio at the inlet to the combustor.

A fuel nozzle assembly 9 as shown in the figures can include a casing 26 adapted to receive a nozzle head 11 which can be selected to provide a fuel cone 10 of desired characteristics. Fuel nozzle assembly 9 is cooperatively joined to casing 1 to direct a spray of fuel 10 into chamber 2 to provide a combustible fuel-air mixture in the chamber. One example of a fuel nozzle assembly 9, as shown in sectional view, FIGURE 2, can be of the air aspirating type where aspirating air is introduced through a cooperative opening 24 and flows through an annular passage 27 to nozzle 11. Nozzle 11 is selected to cause the air stream to be mixed with fuel emitted from conduit 12 to break up the stream of fuel and form an atomized fuel spray to be consumed in chamber 2.

In such applications the spray results from air atomization and it is not necessary to provide a fuel stream at high pressure as is required where the fuel stream is atomized by dynamic forces.

It is desirable to maintain a positive differential in pressure between vapor eliminator 14 and the outlet of conduit 12 to prevent gas flow from chamber 2 to eliminator 14. In applications where the fuel is supplied at less pressure a restriction 28 can be provided in conduit 12 between nozzle assembly 9 and vapor eliminator 14 to increase the pressure drop through conduit 12 and assure the desired positive differential pressure even at the lowest fuel supply rate.

As shown in the example of the figure, a metering valve 23 is often provided to control the flow of fuel to regulate the rate of heat release in the combustor. In operation of such systems the fuel pressure on the upstream side of the metering valve is greater than the pressure on th downstream side so that vapor release is likely as the liquid passes through the mete-ring valve. The released vapor forms vapor bubbles on the downstream side of the metering valve. In the example of the present invention as shown in the figures, the fuel stream including vapor bubbles, is admitted to casing 1-8 and thevapor bubbles, being lighter than the liquid fuel, rise into chamber 16 to displace liquid fuel from the chamber. When a quantity of liquid fuel has been displaced from chamber 16 float 17 drops away from seat '19 so opening 19a is opened to permit the escape of vapor through vapor vent line 13. As the vapor escapes from chamber 16 it is replaced with liquid fuel and float 17 is forced back into seating position against seat 19 by the buoyant forces exerted on float 17 by the liquid fuel. In operation of the combustor the sequence is repeated at regular intervals and the frequency is dependent on the rate of gas release in the liquid fuel.

FIGURE 3 shows another example of a vapor eliminator arrangement in accordance with the present invention which is similar to the apparatus of FIGURE 1 as hereinbefore described. The reference numbers of FIGURE 1 apply to the same elements of the example of FIGURE 3 which provides a series of cooperative communication elements including a fuel source 25, fuel metering valve 23, vapor eliminator 14a which defines a chamber 18, and

fuel nozzle assembly 9 to provide a spray of atomized fuel to a combustion chamber 2 defined by a casing 1. Vapor eliminator 14a of the example of FIGURE 3, advantageously, has no moving parts and includes a conical end section 1412 having a vapor outlet 19 adjacent the top of chamber 18. One end of vapor conduit 13 is communicatively connected to vapor outlet 19a and the other end is communicatively connected to a vapor distributor 29, for example an asbestos wick, wrapped around casing 1. Distributor 29 is in communicative relation with chamber 2 and in the example of FIGURE 3 distributor 29 is wrapped around one row of air inlet apertures 5 so vapor or liquid passes easily from distributor 29 through apertures 5 into chamber 2.

In operation of an apparatus as shown in the example of FIGURE 3 vapor is separated from the liquid fuel and rises to the top of chamber 18 to be conducted to casing 1 through conduit 13. When no vapor is collected at the top of eliminator 14a liquid fuel is supplied to conduit 13 and the diameter of conduit 13 can be very small, for example in the range of 0.03 inch for medium weight fuel, to provide adequate capacity for removal of the relatively small volume of vapor which is normally received from liquid fuel and not large enough to allow passage of a significant quantity of liquid fuel, even at high firing rates. On occasions when liquid fuel flows through conduit 13 the flow rate is dependent on the pressure in chamber 18a and the weight and viscosity of the fuel.

Distributor 29 is heated by casing 1 and any liquid fuel which passes through conduit 13 is vaporized so that the fluid provided to casing 1 f om distributor 29 is primarily gaseous. Distributor 29 can be adapted to receive a small quantity of combustion air to sweep the gases into chamber 2. In applications where distributor 29 includes an asbestos wick the porous nature of the wicking material permits passage of a sufficient quantity of air to sweep the vapors into chamber 2.

The invention claimed is:

1. A liquid fuel burning combustor means comprising casing means defining a combustion chamber for burning liquid fuel, a liquid fuel spray nozzle to supply a spray of fuel to said combustion chamber, means to supply combustion air to said combustion chamber, fuel supply means including a source of fuel for said fuel spray nozzle and means for supplying fuel under pressure to said spray nozzle including: a liquid fuel supply conduit communicating with said fuel spray nozzle and said source of fuel; vapor eliminator means communicatively connected to said conduit means between said fuel source and said spray nozzle to release vapor carried by the stream of fuel supplied by the fuel supply source; and vapor conduit means communicating with the vapor eliminator means and the combustion chamber downstream of said fuel spray nozzle to conduct vapor from the eliminator means to the combustion chamber defined by the casing means.

2. The apparatus of claim 1 wherein said vapor eliminator means includes: a first casing, defining a first chamber, and having a fuel inlet, a fuel outlet, and a vapor outlet means disposed so vapors released from said liquid fuel pass therethrough; a second casing defining a second chamber, and having a vapor inlet communicating with said vapor outlet of said first chamber so vapors which escape from said first chamber pass to said second chamber and a vapor outlet from said second chamber; float means disposed for free movement in said second chamber where the specific gravity of said float means is such that said float means rises to the upper surface of said liquid fuel but falls in a gaseous atmosphere; and, means to retain said float means in aligned relation with said vapor outlet of said second chamber so said float means rises with increasing level of liquid fuel in said second chamber to close off said vapor outlet of said second chamber when said second chamber is substantially filled with liquid fuel. 4

3. The apparatus of claim 1 including metering means disposed in said fuel supply conduit between said fuel supply means and said fuel spray nozzle where said vapor eliminator is communicatively disposed in said fuel supply conduit between said fuel metering means and said fuel spray nozzle.

4. The apparatus of claim 1, including fuel flow restricting means in said fuel supply conduit between said vapor eliminator and said fuel spray nozzle.

5. The apparatus of claim 1 wherein said fuel spray nozzle includes means to mix a stream of air with said fuel supplied to said fuel spray nozzle to form a fuel spray.

6. The apparatus of claim 1 wherein said casing means includes an elongate cylindrical tube having perforations therein for admission of combustion air to said combustion chamber and said vapor conduit means includes fuel distributor means adjacent said perforations of said casing to distribute fluid carried by said conduit means through said perforations into said combustion chamber downstream of said spray nozzle to supply such vapor to said combustion chamber.

7. The apparatus of claim 6 wherein said distributor means includes porous asbestos material.

References Cited UNITED STATES PATENTS 1,344,421 6/1920 Manker 158-69 2,458,042 1/ 1949 Williams 158-36 2,632,499 3/1953 Getz et a1. 158-36 3,228,447 1/ 1966 Heberlein 15 8-5 3 JAMES W. WESTI-IAVER, Primary Examiner. 

